As IT shops gain expertise in virtualized applications, they can also get a better handle on load balancing and availability—once the domain of clustering solutions.

As enterprises become more involved in virtualizing their application servers, they are finding that virtualization can deliver more than just better utilization of their computing resources. High availability and near-term server failover, previously the province of clustered servers, are now available in virtualization applications for less money and less hassle than had been the case with pure-play clustering applications.

The combination of better resource use, reduced power and cooling in the data center, and more manageable applications delivery has made virtualization a very popular solution. As IT shops gain more expertise in delivering virtualized applications, they can also get a better handle on the kinds of load balancing and availability issues that once were the exclusive domain of clustering solutions.

Indeed, virtualization continues to be complementary to—and is sometimes a less expensive replacement for—some applications that don’t require the up-to-the-nanosecond transaction-level failover that clustering provides.

“We are at a point where constantly changing business requirements, coupled with perennial pressure on IT to lower costs, are forcing the two to come together and scale infrastructure resources in and out in real time based on workloads,” says Anurag Chauhan, a consultant on data center technologies with Accenture in Chicago. “This is creating an architecture in which resources are virtualized, but also aggregated or clustered for higher processing loads through smart policies.”

The intersection of both technologies has produced a big business benefit that is widening the appeal: disaster-recovery protection. “In the past, you needed to buy another physical server in case the primary machine went down,” says Bob Williamson, a senior vice president at Steeleye, a specialized virtualization vendor. “By using virtualization and hosting these servers at a remote location, enterprises can use the machines if their data center goes out. That lowers the entry cost for deploying wider-area disaster recovery and opens up this protection to a whole new set of companies that haven’t been able to consider it before.”

Clustering may still be required in specific cases. “If you are using some sort of transaction-processing system where you need to preserve the state of the server, then you are going to need some special-purpose clustering solution,” says Ken Oestreich, director of product management for Cassatt, which makes automation tools for managing virtualized sessions. “But the majority of the applications in the data center don’t need this level of granularity.”